As wireless communication systems continue to grow in popularity, they also continue to grow in diversity. While at the present time various types of third-generation (3G) wireless networks are commercially deployed throughout many parts of the world, fourth-generation (4G) wireless networks are also beginning to be deployed. These systems include, but are not limited to, Code Division Multiple Access (CDMA®), Worldwide Interoperability for Microwave Access (WIMAX®), Universal Mobile Telecommunications System (UMTS), Long Term Evolution (LTE®), or other protocols. Each type of 3G and 4G wireless network may employ different types of physical layer modulation and link-layer signaling, and may operate using different carrier frequencies. For example, a first base transceiver station (BTS) from a 3G wireless network may radiate on a first carrier frequency to define a first wireless coverage area. Additionally, a second BTS from a 4G wireless network may radiate on a second carrier frequency to define a second wireless coverage area. The first and second carrier frequencies can be chosen with an appropriately large guard band so that communications using the first carrier frequency do not interfere with communications using the second carrier frequency.
As these 3G and 4G systems continue to be deployed, it is unlikely that there will be one ubiquitous, standard wireless network technology. Instead, wireless communication devices (WCDs) such as cell phones, may support multiple 3G and/or 4G technologies in order for users of these devices to maximize their wireless coverage. Thus, it is desirable for these WCDs to be able to support vertical handoffs from a first type of wireless network (e.g., a 3G wireless network) to a second type of wireless network (e.g., a 4G wireless network), and/or vice versa. In this way, a WCD can maintain wireless network coverage even if either the first or second type of wireless network is not within range of the WCD.
Ideally, the WCD can perform vertical handoffs without interrupting any of its ongoing communication sessions. However, this may be a challenge when the WCD is configured to use different forms of identification to access the different types of networks.